Preparation of cold swelling starch-aldehyde compositions



Patented June 6,1950

4' y 2,510,748 a PREPARATION OF GOLD SWELLING van der Meer, Haren,Netherlands, assignors to Naamlooze Vennootschap: W, A. ScholtensChemische Fabrieken, Groningen, Netherlands,

a corporation of the Netherlands No Drawing. Application Ncveinbe'r l,Se

rial N0."707,326. 1945 40mins; (c1. sec-233.3)

U. s. Patent No. 2,246,635 describes a process of manufacturing starchproducts the solutions of which when dried will produce water resistant.layers, which process is characterized by adding to cold swellingstarch before or during the manufacturing thereof an aldehyde,particularly formaldehyde, or a substance producing aldehyde bydecomposition. The patent also relates to the manufacture of solutionsof such starch products.

For the manufacture of cold swelling starch a mixture of starch or astarch derivative with a limited quantity of water is heated on a rotarydrum to'a temperature above the gelatinizing point, while pressing themass under mechanical pressure to form a thin layer, which is dried si-1 ing, or swelling in cold water. Insoluble products are only formed bydissolving the same in water and drying the solution by heating,preferably in the presence of a catalyst and subsequently heating thesame for some time to a high temperature if necessary. It is thereforepossible to obtain water resistant layers in a very simple manner by theuse of the said starch products, so that they will constitute valuablefinishing, sizing and binding agents and adhesives.

The formation of the insoluble products with formaldehyde is most likelybased upon the formation of bridges, e. g. methylene ether bridges,between thestarch molecules, this process bein accelerated by thepresence of catalysts, more particularly acids.

U. S. patent application Serial No. 707,321, describes an improvement ofthe said process which consists in that the heating process for thepreparation of the cold swelling starch is effected in a neutralor analkaline medium.

In actual practice commercial formalin was used for the preparation offormaldehyde-cold swelling starches according to U. S. Patent No.

2,246,635 and commercial formalin as a rule conportion of acid was thecauseoi-a certain con- 9 respectively.

In the Netherlands June 18,

densation and consequently of a reduction of the solubility during theprocess of manufacturing the cold swelling starch, so that it was onlypossible to obtain preparations with good swelling properties, whenadding less than 10% of formaldehyde, calculated on the starch. If,according to U. S. patent application Serial No. 707,321 the coldsWe11iIlg starch process is carried out in a neutral or alkaline medium,it will be possible still to obtain readily soluble aldehyde-coldswelling starches with'considerably larger proportions of formaldehyde,e. g. 40%.

It has now been found that even in a slightly acid medium i. e. with apH between 5 and 7 with a proportion of aldehyde of more than 10 it willbe possible to obtain readily soluble products, if the cold swellingstarch process is carried out at temperatures below 0. Although in US.

patent No. 2,246,635 and in U. S. patent applica tion Serial No. 707,321it is not positively stated that the treatment is effected at highertemperatures, both cases refer to the ordinary cold swelling starchprocess, in which the starch layer on the cylinders during the dryingtreatment ac.- quires a temperature of about -l70 C. It has now beenfound that the temperature during the cold swelling starch processgreatly influences the solubility of the dry product and that thissolubility decreases in proportion to the increase in temperature duringthe drying treatment. 7 If the process is carried out at lowtemperatures, e. g. by employing cylinders having a steam pressure of2-3 atm., there will be formed even in a slightly .neutral or alkalinemedium will have a favourable influence; the effect is, however, of lessimportance, since in this case there will be formed, even at highertemperatures products the solubility of which is satisfactory.

The influence of the temperature during the cold swelling starch processon the solubility of the final products is demonstrated by the followingexperiments:

Mixtures of potato starch and formaldehyde in a proportion of 20%,calculated on the starch, were submitted to the cold swelling starchprocess at pH-values of 5, 7'and 10, and with steam pressures in thecylinder of 2 and of 8 atm., corresponding to temperatures of about 130and pounds.

Mixtures having a pH value of 7 or of. 10 re-..

spectively will at a steam pressure ofiz'atmospheres give products thatare highly soluble and will swell quickly. If, however, the steam pres:

sure is increased to 8 atm. the final productswil-l swell far moreslowly, but still completely. I

Summarizing, it may therefore be stated that in a. slightly acid medium(pH 5-7) and with larger proportions of an aldehyde, soluble productsare only obtained when the drying treatment 'is carried out at a lowtemperature, whereas in a neutral or an alkaline medium, even at hightemperatures,'solublealdehyde-cold swelling starches are formed which,however, will swell or dissolve more slowly than preparations formed atlower temperatures in otherwise similar conditions;

The manufacture of the aldehyde-cold-swellin'g :starches may be effectedon the known on'eor two-cylinder drying devices, at such steam pressuresthat the'temperature of the layer wil1-not exceed, e. g. 130 'C. One'mayalso use vacuum drum drying devices by means of which it'is possible tocarry out the cold swelling starch'manufacturing process even attemperatures below 100 C.

For particulars'regarding the manufacture and the use of .theformaldehyde-cold swelling starches, we may refer to U.'S.PatentNo'.'2,246,'- 5635 and U; S. patentapplication Serial No. 707,321 .inwhich the use of higher temperatures is considered. The aldehyde e..g.may be used inthe shape of compounds that will produce'the aldehydebyxdecompositiomisuch'as e. g. hexamethyl- -ene tetramine,paraformaldehyde or trihydroxy :methylene, while instead of nativestarch decomposed starches, such as soluble starch,..may :be used. Inorder to promote the reaction acids-or acid producing compounds arepreferably used. .This catalyst may already be present in the dryproduct, which may be accomplished by manufacturing two cold swellingstarch preparations, one or which contains the aldehyde, while the othercontains the catalyst.

One may also add substances which will form synthetic resin likecondensation products with the aldehyde, such. as e. g. phenols or aminocomaccording to the invention are the same as for those described in U.S. Patent No. 2,246,635 and -U.- S. patent application Serial No.707,321.

As first materials for the process according to the invention-starchderivatives in the broadest senseof the term may be used and thesaidterm does not only include the-native starches "and hydrolysis and/oroxidation products of starch, but e. g. also ethers and/or esters ofstarch containing free hydroxyl groups.

The invention will be explained-with the aid of the following examples.

Example 1 1000 parts by weight of potato starch are suspended inan'lixture of 500'parts by volume of-a 40% by volume solution offormaldehyde and 1000 parts by volume of -water. This-suspension is:giv-

The possibilities for using the products 1' lution and subsequentlyconverted into cold swelling starch on a heated, rotating cylinder, inthe usual manner but at a, temperature of approximately '120-130 C. Thecold swelling starch thus formed. will dissolve completely in 8-10 partsof cold water to a viscous, smooth and transpar ent solution.

If the cold swelling starch process is carried out Jat170-180 C., whileconditions are the same in other respects, one will obtain an insolubleproduct that willswell' inwater only to a very limited degree.

I Example 2 The process is carried out in the same manner as accordingto Example 1, but the suspension is converted into cold swelling starchat a pH of 7. One obtains a formaldehyde-cold swelling starch that willquickly swell or dissolve in 8-10 parts of cold water to a viscous,transparent, perfectly smooth solution.

If the cold swelling starch process is carried out at a temperature ofabout 180 0., one will obtain, under conditions similar in otherrespects, a product which is still soluble in cold water, but

which will swellior dissolve very slowly and which with 8 parts of waterwill produce a very viscous paste of a coarse structure.

Example 3 1000 parts by volume of a 40% commercial formaldehydesolutionare diluted-with 500 parts "by volume of water, after which 1000 partsby 'weight'oi tapioca flour are suspended in thissolution. Thesuspension is givena pH of 5.5 and then converted into cold swellingstarch-at a temperature of approximately C. The hydroxy- "methyl etherof starch-thusprepared will readily dissolve in 0-12 parts of cold waterto a viscous,

transparent and smooth solution.

Example .4

Operations are carried outin-the same manner as according to'Example3,'but the suspension submitted to theprocess oim'anufacturing coldswelling starch has a pH of 9. In this manner one obtains aformaldehyde-cold swelling starch which is easily soluble in cold waterand produe-es perfectly smooth pastes. 'If, however, the

cold swelling. starchproce'ss is carried outunder starch preparations;the. solutions of which when dried will produce water '1' resistantlayers, comprising adding to a starch productia limited quantity ofwatenand at least 10% 1of 'analdehyde, :calculated on the weight ofthedry starch prod uct, adjusting the mixture tov apH of at .least 5 andheating the same one. rotating cylinder to a temperature above the==gelatinizing point of starch "but. not exceedin C.,' while pressing ithe mass under mechanical :pressure toform a thin layerwhich issimultaneously dried and sub- .seguentlycom-minuted.

A'pro cess asset forth inclaim l in which the-aldehydeis addedin'the-form of-an; aldehyde- ,producing substance. v

3; A-proeess asset iorth-in claim '1 wherein en a pH of 6 by means ofdilute lcaustlcisoda so-r" sa-id a-Idehydeisformaldehyde,--

5 4. A process as set forth in claim 1 wherein UNITED STATES PATENTS thestarch, aldehyde and water has a pH value Number Name Date of between 5and 602,697 Classen Apr. 19,1898 JAN LOLKEMA. a 826,881 French Apr. 12,1938 WILLEM ALBERTUS VAN DER MEER. 0 2,099,765 Freiherr et a1. Nov. 23,1937 2,417,611 Pierson Mar. 18, 1947 REFERENCES CITED OTHER REFERENCESThe follbwing references are of record in the Blanksma Rec T Chim" 43(1929),

file this Patem 10 351-360, 10 pages.

1. A PROCESS OF MANUFACTURING COLD SWELLING STARCH PREPARATIONS, THESOLUTIONS OF WHICH WHEN DRIED WILL PRODUCE WATER RESISTANT LAYERS,COMPRISING ADDING TO A STARCH PRODUCT A LIMITED QUANTITY OF WATER AND ATLEAST 10% OF AN ALDEHYDE CALCULATED ON THE WEIGHT OF THE DRY STARCHPRODUCT, ADJUSTING THE MIXTURE TO A PH OF AT LEAST 5 AND HEATING THESAME ON A ROTATING CYLINDER TO A TEMPERATURE ABOVE THE GELATINIZINGPOINT OF STARCH BUT NOT EXCEEDING 140*C., WHILE PRESSING THE MASS UNDERMECHANICAL PRESSURE TO FORM A THIN LAYER WHICH IS SIMULTANEOUSLY DRIEDAND SUBSEQUENTLY COMMINUTED.